Combined piston and plunger-rod



A. LEVEDAHL.

COMBINED PISTON AND PLUNGER ROD.

APPLlCATlON FILED JU NE 28,1920.

Patented June 7, 1921.

m/wzZ' of jxewewma UNITED STATES PATENT OFFICE.

TOOL COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

COMBINED PISTON AND PLUNGER-ROD.

Specification of Letters Patent.

Patented J une'7, 1921.

Original application filed July 30, 1919, Serial No. 314,374. Divided and this application filed June 28,

' 1920. Serial No. 392,179.

To all whom it may concern:

Be it known that I, AXEL LEVEDAHL, a citizen of the United States, residin at Aurora, in the county of Kane and btate of Illinois, have invented new and useful Improvements in Combined Pistons and Plun more particularly pointed out in the ap-.

pended claims.

In the accompanying drawings Figure 1 is a side elevational view of a pneumatic sand rammer with the piston and its rod and barrel in section to illustrate the features of my invention applied thereto;

Fig. 2 is a side view, on an enlarged scale, of the piston and its plunger rod, removed from the barrel of the tool;

Fig. 3 is a transverse sectional view taken on line 33 of Fig. 2; and

Fig. '4 is a transverse sectional view taken on line 44 of Fig. 1.

In the drawings, I haveshown the features of my invention applied to the working parts of a pneumatic tool, which, as

illustrated, is a pneumatic sand rammer of I the floor type as described and claimed in my co pending application Serial No. 314,374, filed July 30, 1919, and of which the present application is a division.

As illustrated herein, a tool of that character has a barrel 1, on the inner end of which is screwed a valve housing or head 2. The barrel has the usual bore 3, in which reciprocates a piston 4 having a piston rod 5 projecting beyond the outer end of the barrel through a stufling box structure located in that end of the barrel. To the outer end of the rod is applied a stamper or peen 6, required for tools of this character. The barrel has passages 7, as usual, for the operating fluid, the admission and exhaust of which to and from the barrel on opposite sides of the piston being controlled by a valve (not shown) of the differential pressure area type in the head 2. Connected to the head 2 is a throttle stem 8 in alinemeut with the barrel and through which live air enters the barrel and controlled by a self closing throttle valve (not shown) in-said stern and opened bymo-ving a lever 9 pivoted flutes 10, 10, forming key-ways, made in accorolance with my invention and extending lengthwise of the rod and spaced apart circumferentially, preferably equal dlstances, as shown in Figs. 3 and 4. The stuffing box structure, as shown in Fig. 1, has a packing of (gaskets 11, 11 compressed between inner an outer rings 12, 18, the outer ring 13 having an outwardly projecting radial tongue 14 to engage in a groove 15 in the barrel to hold the ring against rotation. The gaskets are made to fit in the flutes 10,

'10 in the rod, and when the gaskets are compressed between the rin s by screwing up the nut 16, the gaskets Wlll be held from rotation and likewise hold the rod and its piston from turnin The flutes 10 eing concave have curved keying surfaces and give more cylindrical area to the rod than would be given should these key-ways be formed by flat surfaces at the same depth as the flutes. Thus, there is not only more surface on the cylindrical part of the rod, but greater area is given to the rod and therefore more strength and stiffness. Moreover, the flutes 10 being curved,

present a better keying surface than would be possible with the flat surfaces, as a curved surface is more radial. The flutes, in addition, are more easily ground than the common straight sided key slots, and further permit the packing to be readily formed to fit in the flutes. Three flutes 10 are used to balance the rod and make it stiff each way.

The piston 4 is made hollow to reduce its Weight, and its inner end is made open and closed by a cap 17 applied in accordance with my invention. The piston is provided at such end and on the inside thereof with an undercut groove or recess 18, the base 19 of which is substantially flat and forms a.

shoulder or seat for the cap. In forming the groove lflfthe' thickness of the piston wall at the outer edge of the groove is less than the wall thickness through the shoulder 19, thus making the diameter at the outer edge less than the diameter at the inner edge. The cap 17 'is made concave and while in that form has a diameter to slip past the outer edgeof the groove and come to rest on the seat or shoulder 19. After being placed in the groove, the cap 17 is pressed flat to increase its diameter and fit tightly in the groove, as shown in Fig. 1. This operation of flattening out the cap makes an air tight fit, and saves air, as none is allowed to enter the hollow piston. The cap is made from soft steel and not hardened and is not required to be, as it is not a wearing surface. The cap is provided on its under side with an integral projection 20 to allow centering for grinding. The cap is comparatively light in weight, cheap to make,

and easy to apply, as no screw threads are required, nor any additional plugs or keys required to lock or hold it in place, as the undercutting of the groove and flattening the cap in place provides a tight and secure fit. Moreover, the cap does not work loose, as is the case with a screw-threaded plug, and furthermore the piston may be hardened throughout and need not be left soft to drill holes therein for keys for these screw plugs, thus avoiding annealing the inner end of the piston after the cap is applied, as has been the practice heretofore. Thus no soft parts are left in the piston to cut in the barrel.

While I have shown and described herein the features of my invention as being applied to parts in a pneumatic sand rammer, it is to be of course understood that my invention could equally as well be applied to pneumatic tools of other kinds.

I I claim as my invention:

1. In a pneumatic tool, the combination of a barrel having a stufling box in the outer end thereof, and a reciprocable piston rod in said barrel and extending beyond the outer end of said barrel through said stuffing box, said rod being provided with a plurality of longitudinally extending, concave flutes, and said stufling box being provided;

with means for engaging said flutes to hold the rod against rotation.

2. In a pneumatic tool, the combination of a barrel having a stuffing box in the outer end thereof, a reciprocating piston in said 1 barrel, a rod connected with said piston and extending beyond the outer end of the barrel through said stuffing box, said rod being provided with a plurality of longitudinally extending flutes curved transversely to provide a keying surface, portions of which being approximately radial, and said stuffing box having parts extending into and fitting providedwith a plurality of longitudinallyextending, concave flutes, spaced apart circumferentially and having portions of the curved surface substantially radial for providing a keying surface.

4. In a pneumatic tool, a hollow cylindric member therein having one end made open and there provided on the inside thereof with an annular undercut groove opening through said end, and an annular concave cap inserted in said open end and adapted to be flattened out to engage in said groove and close the open end of said member.

5. In a pneumatic tool, a hollow cylindric member therein having one end made open and there provided on the inside thereof with an annular undercut groove opening through said end with the diameter at the outer edge of the groove less than the diameter of the groove at its inner edge, and an annular concave cap having a diameter to pass the outer edge of'said groove and adapted to be flattened out to engage in said groove and close the open end of said mem- 6. In a pneumatic tool, a hollow cylindric member therein having one end made open and there provided on the inside thereof with an annular undercut groove opening through said end with its base substantially flat and its outer edge of a diameter less than its edge at said base, and an annular concave cap having a diameter to pass the outer edge of said groove and seat on the base thereof and adapted to be flattened out to engage tightly in said groove to close the open end of said member.

7 In a pneumatic tool, ahollow reciproinside thereof. with an annular undercut groove having its outer edge of a diameter less than the inner edge of the same, wand an annular concave cap made of soft metal and having a diameter to pass the outer edge of said groove and adaped to be flattened. out to increase, its diameter and en gage tightly in said groove for closing the inner end of said piston.

In testimony that I claim the foregoing as my invention, I affixv my signature this 24 day of June, A. I). 1920.

/AXEL LEVEDAHL. 

